What principally distinguishes ījāz al-qaṣr from ījāz al-ḥadhf?

Musāwāt and Ījāz al-Qaṣr: Proportionate Wording and the Rhetoric of Qiṣāṣ

• Qaṣr must be imperative and ḥadhf prohibitive
• Qaṣr only occurs in poetry and ḥadhf only in prose
• Qaṣr uses rich meaning in the expressed wording; ḥadhf recovers an omitted element through context
• Qaṣr always uses more words